Hydrogen is a useful gas. Whether you want to float an airship, fuel a truck, or heat an industrial process, hydrogen can do the job. However, producing it is currently a fraught issue. While it can be produced cleanly using renewable energy, it’s often much cheaper to split it out of hydrocarbon fuels using processes that generate significant pollution.
Although we take a lot of scientific knowledge for granted today, each of the basics – whether it be about light, gravity, mass or the shape of the Earth – had to be theorized and experimentally verified. In the case of gravity, as far back as around 500 BCE the Ionian Greek philosopher Heraclitus theorized on the balance created by what we came to call ‘gravity’. Later, the Greek philosopher Aristotle coined his own postulations and Greek physicist Archimedes did research that led him to discover the center of mass. Centuries later, the Roman engineer and architect Vitruvius argued for the concept of specific gravity rather than mass alone.
Da Vinci’s sketch and the Caltech experiment replicating it.
Although scientific pursuits in this area ground to a halt in Europe during medieval times, the Renaissance saw a renewed interest in the topic, with newly published research performed on Leonardo da Vinci‘s notes showing that he appears to – unsurprisingly – have also created a number of experiments aimed at determining the properties of gravity. One of the major limitations of the 15th century was that many of the basic scientific tools we have come to rely on since the 19th century such as accurate clocks, along with many other products of advanced alloys and metallurgy simply did not exist. Da Vinci’s experiment in this context is nothing if not ingenious in its simplicity.
By the time of the European Renaissance, the Aristotelian concept of gravity as solely a factor of an object’s mass was dismissed by many in favor of a model that saw the motion of an object affected by its velocity and mass, also influenced by works published by Persian scholars. When Da Vinci set up his experiment, he focused specifically on the acceleration of the falling objects by pouring a large number of granules or possibly water droplets from a pitcher which was being pulled along a straight path. He theorized that if the pitcher was being accelerated at the same rate as the objects are accelerating due to gravity, it’d create a isosceles right triangle.
When the researchers ran his experiment and compared Da Vinci’s notes on the results, they realized that although he had made a mistake in his model, at the small scale this would not have affected the results, making it valid and an early precursor to what later be published by Isaac Newton in the 17th century.
We’ve all tangled with unwelcome plant life at one point or another. Whether crabgrass infested your lawn, or you were put on weeding duty in your grandfather’s rose patch, you’ll know they’re a pain to remove, and a pain to prevent. For farmers, just imagine the same problem, but scaled up to cover thousands of acres.
Dealing with weeds typically involves harsh chemicals or excessive manual labor. Lasers could prove to be a new tool in the fight against this scourge, however, as covered by the BBC.
During the Middle Ages much of Ancient Greek and Roman scientific, legal and similarly significant texts written on parchment were commonly erased, mostly because of the high cost of new parchment and the little regard given to these secular texts. Although recovery attempts of the remaining faint outlines of the old text has been attempted since at least the 19th century, these often involved aggressive chemical means. Now researchers have managed to recover the text written by Ptolemy on a parchment that suffered such a previous recovery attempt.
The term for a parchment and similar on which the existing text was washed or scraped off is a palimpsest, via Latin from Ancient Greek παλίμψηστος (palímpsēstos, from παλίν + ψαω = ‘again’ + ‘scrape’). In the case of this particular treatise, it is part of L 99 sup which is kept at the Biblioteca Ambrosiana in Milan, Italy. This collection contains fifteen palimpsest parchment leaves previously used for three Greek scientific texts: a text of unknown authorship on mathematical mechanics and catoptrics, known as the Fragmentum Mathematicum Bobiense (three leaves), Ptolemy’s Analemma (six leaves), and a so far unidentified astronomical text on six leaves.
Outermost six rings of the meteoroscope, not to scale. Nh, Sh, Eh, and Wh are cardinal points of the horizon; Ne and Se are the north and south celestial poles; Nz and Sz are the north and south poles of the ecliptic; and Z is the zenith. (Gysembergh et al., 2023)
It is this last text that has now been identified, courtesy of work by Victor Gysembergh and colleagues. Whereas 19th century palimpsest recovery attempts by Angelo Mai involved reagents, during the 20th century ultraviolet illumination became the preferred method, followed by similar non-destructive analysis methods. For this study UV fluorescence and multispectral reflectance imaging was employed, which allowed for significant more of the original Greek text to be uncovered. Most notable, this revealed Ptolemy’s treatise on the Meteoroscope, which is an instrument for measuring the position, length, and direction of the apparent path of a shooting star.
This new recovery builds upon text previously recovered by other researchers since Mai’s attempts, and fills in more details, although it must be noted that not all of the text has been recovered. It’s hoped that in future imaging sessions more can be recovered of this irreplaceable text, that like so many of its kind nearly got destroyed during Europe’s darkest era.
(Top image: Ambrosianus L 99 sup., p. 190, ll. 14–23, UV fluorescence image by Lumière Technology. Upside-down Latin overtext in dark brown and Greek undertext in light brown.)
At the level pursued by many Hackaday readers, the advent of affordable 3D printing has revolutionised prototyping, as long as the resolution of a desktop printer is adequate and the part can be made in a thermoplastic or resin, it can be in your hands without too long a wait. The same has happened at a much higher level, but for those with extremely deep pockets it extends into exotic high-performance materials which owners of a desktop FDM machine can only dream of.
The alloy receives some of its properties because of its oxide-dispersion-strengthened composition, in which grains of metal oxide are dispersed among its structure. We’re not metallurgists here at Hackaday, but we understand that the inconsistencies in the layers of metal atoms caused by the oxides in the crystal structure of the alloy leads to a higher energy required for the structure to shear.
While these particular materials might never be affordable for us mere mortals to play with, NASA’s did previously look into how it could greatly reduce the cost of high-temperature 3D printing by modifying an existing open source machine.
If one is serious about testing the stiffness of materials or parts, there’s nothing quite like doing your own tests. And thanks to [JanTec]’s 3-Point Bending Test rig, there’s no need to reinvent the wheel should one wish to do so.
The dial caliper can be mounted to a fixed height, thanks to a section of 3030 T-slot extrusion.
Some simple hardware, a couple spare pieces of 3030 T-slot extrusion, a few 3D-printed parts, and a dial indicator all come together to create a handy rig that will let one get straight to measuring.
Here is how it works: stiffness of a material is measured by placing a sample between two points and applying a known force to the middle of the sample. This will cause the material to bend, and measuring how far a standardized sample deforms under a known amount of force (normally accomplished by a dial indicator) is how one can quantify a material’s stiffness.
When a material talks about its Young’s modulus (E) value, it’s talking about stiffness. A low Young’s modulus means a material is more elastic, a high value means the material is more stiff. (This shouldn’t be confused with strength or toughness, which are more about resistance to non-recoverable deformation, and resistance to fracture, respectively.)
What if you could tweak the recipe on ice cream to keep it frozen at higher temperatures? The idea comes from massive conglomerate Unilever. Among other things, the brand owns a wide variety of ice cream brands, from Ben & Jerry’s to the Magnum and Cornetto lines. Instead of running freezers at the industry standard of -18 °C (0°F), the company is experimenting with upping the temperature to -12 °C (10 °F) instead.
First off, you’d save a lot of electricity. Thanks to the way the industry works, the company actually owns the vast majority of the three million or so display freezers that are used to sell its stock to customers. Running at a higher temperature could slash the freezer’s energy use by 20% to 30%, according to the company’s calculations. The company also estimates that the energy used by these freezers makes up around 10% of its total greenhouse gas footprint, so it’s better for the environment too.
Of course, there’s savvy commercial reasons behind the idea. Unilever had noticed its ice cream sales dropping in 2022. The company believes this was in part due to retailers unplugging their freezers earlier than usual as winter approached, due to high energy bills. If the company’s freezers aren’t humming, they’re doing less business. If shaving down the freezer’s energy use helps retailers keep them plugged in and the lights on, that’s a net bonus to the company’s bottom line. It could also make their freezers unhospitable places for rival products, giving them an edge in the marketplace.
But this is all business intrigue. Let’s instead take a deeper look at ice cream.
